Solar sail topology variations due to on-orbit thermal effects

The objective of this research was to predict the influence of nonuniform temperature distribution on solar sail topology and the effect of such topology variations on sail performance (thrust and torque). Specifically considered were the thermal effects due to on-orbit attitude control maneuvers. Such maneuvers are expected to advance the sail to a position off-normal to the sun by as much as 35 deg; a solar sail initially deformed by typical pretension and solar pressure loads may suffer significant thermally induced strains, due to the nonuniform heating caused by these maneuvers. This on-orbit scenario was investigated through development of an automated analytical shape model that iterates many times between sail shape and sail temperature distribution before converging on a final coupled thermal-structural affected sail topology. This model uses a validated geometrically nonlinear finite element model and a thermal-radiation subroutine. It was discovered that temperature gradients were deterministic for the off-normal solar angle cases, as were thermally induced strains. Performance effects were found to be moderately significant but not as large as initially suspected. A roll torque was detected, and the sail center of pressure shifted by a distance that may influence on-orbit sail control stability.